Women hear a lot about hormones. From the time we hit puberty to well past menopause, there's a nearly constant undercurrent of information and implication (we're referring to all those PMS jokes) that doggedly follow our every physiological move. Men, however, are often squarely in the dark when it comes to knowing exactly what their own chemical compounds are doing -- or not doing -- while coursing through their veins.

The truth is, male and female hormones are very much alike; in some cases, estrogen and testosterone compounds are set apart by a single atom. From moods to muscles, men are just as affected by hormones as we are. And, keeping male hormones in the proper balance offers a lot of benefits. Not only does the right amount of testosterone chase away dour attitudes, but it also translates into better sexual performance, improved fitness and increased overall health. Wondering if your guy is on the right track? We've got 10 things you should know, starting on the next page.

10

Balance is Crucial

You've probably heard of testosterone and, while it certainly plays an important role in men's health, it's only one of several hormones at work. Male-produced hormones each fuel a complex endocrine system that sends signals to organs throughout the body, from the brain to the testes. These hormone levels change from hour to hour [source: WebMD]. And, if hormones get out of balance or begin to decline (which happens at about age 40, sometimes sooner), the body begins to store too much fat and prompts a person to eat when he is not really hungry. This slippery slope leads to metabolic syndromes, such as diabetes. A hormone imbalance also hampers a man's ability to fight stress, while making him feel exhausted, anxious, irritable and less interested in sex [source: Hurlock]. If that doesn't sound like a cocktail for disaster, we don't know what does. So, what role does testosterone play in this cast of hormones? Maybe not the one you think. Find out why, on the next page.

9

You Can't Blame Everything on Testosterone

Testosterone: It's a term often associated with road rage and televised wrestling championships. The truth is, testosterone doesn't really create overtly negative behaviors. So, if the man in your life has a penchant for screaming at drivers who cut him off in traffic, hormones aren't necessarily to blame. However, testosterone does affect the size and strength of muscle and bone -- so it could offer benefits if the screaming match progresses into fisticuffs. Testosterone -- one of several male hormones classified as androgens -- is also a prime player in sexual appetites and sperm production. It's also why men usually have deeper voices than women, as well as the ability to grow a beard or mustache [source: Shmerling].

Testosterone can even impact the way a man feels about technology. Researchers at the University of Bath in England discovered pre-natal testosterone exposure affects the way a brain develops and, later in life, this allows gray matter an easier grasp of new technology. Turns out, people with high exposure to testosterone in utero were more inclined to embrace technology; those with lower levels of exposure had more computer-related anxiety [source: PhysOrg.com]. Despite testosterone's well-defined roles in men's health, it's a hormone women have, too. Find out more, next.

Testosterone and Aggression

Testosterone is a sexual hormone with a bad-boy reputation. But does it really cause aggression and increased risk-taking? No, say researchers. Biologically speaking, an influx of testosterone simply makes men more aware of their societal status in a complex societal system, which in turn, encourages them to act out dominant roles [source: Science Daily].

8

Testosterone Isn't Just for Men

Women produce testosterone naturally, secreting the hormone from their ovaries and adrenal glands. It's key in ovarian function, which means that women with proper testosterone levels ovulate regularly. Testosterone also improves bone strength, elevates mood and is even thought to stimulate sexual appetites [source: Shmerling]. According to a recent study by scientists in Italy, women who received small doses of extra testosterone reaped a number of benefits [source: Hunter]. In addition to greater muscle strength and increased endurance, testosterone supplements also reduced insulin resistance, which is a precursor to diabetes. The news is especially promising for older women who, like men, experience a decline in hormone production as they age.

But striking just the right balance of male hormones is tricky business, especially for women who'd like to increase their pregnancy odds -- which we'll explore on the following page.

7

Thyroid Hormones Decline with Age

There are a host of hormones that can affect a man's emotional and physical well-being, but one in particular becomes less reliable after age 60. Thyroid hormone declines with age, and a number of recent studies demonstrate a link between waning thyroid hormones and sexual dysfunction. This includes erectile dysfunction, which is the inability to maintain penile erection [source: Krassas]. The most common problems of low thyroid, or hypothyroid, also include declining sexual desire, but it doesn't stop there. Classic symptoms include weight gain, hair loss, memory loss, constipation and rough, dry skin [source: San Diego Sexual Medicine]. The good news is that with synthetic hormone replacement, these symptoms -- including erectile dysfunction caused by hypothyroidism -- usually reverse themselves.

Female Fertility and Male Hormones

The ideal amount of female-produced testosterone is critical to becoming pregnant. In the ovaries, testosterone is converted to estrogen, which allows egg-containing ovarian follicles to retain their optimum qualities [source: Science Daily]. If a woman has high levels of testosterone, it creates poor egg quality and decreases pregnancy odds.

6

Too Much Testosterone is Bad for Both Sexes

When a woman has too much testosterone in her system, there are a few telltale symptoms: acne, irregular periods and weight gain. Elevated testosterone levels also cause acanthosis nigricans, a condition in which patches of dark skin appear on the back of the neck or other areas. It can also cause hirsutism, which is extra hair on the face or other parts of the body where thick hair normally doesn't grow [source: Center for Young Women's Health]. And, in the case of opposite-sex twins, testosterone exposure can even affect the odds a woman will someday marry. Researchers in England discovered adult female twins were 15 percent less likely to marry if they had a male twin and were 25 percent less likely to have children -- all attributed to in utero testosterone exposure [source: ScienceDaily].

When men have too much testosterone coursing through their veins, problems also arise. Too much of the chemical compound, and it can cause liver disease, while boosting levels of bad cholesterol and lowering levels of good cholesterol -- which can lead to heart disease. And, as excess testosterone naturally undergoes a chemical conversion within the body, it can cause acne and male-pattern baldness [source: Harvard Medical School].

The Link Between PCOS and Testosterone

Elevated testosterone levels are often present in women with polycystic ovarian syndrome (PCOS). This condition affects women of childbearing age and produces symptoms including weight gain, thin hair, acne, irregular periods and, more seriously, infertility [source: WebMD]. Fortunately, the condition often can be treated with hormone-regulating medications.

5

Male Hormones can Increase Cancer Risk

There are plenty of benefits to a plentiful amount of male hormone, such as increased energy, alertness and muscle tone. Unfortunately, hormones also play a role in abnormal cell reproduction -- particularly for men. Cancer cells in the prostate, for example, are fueled by testosterone. This makes the indiscriminate use of testosterone creams and other replacement therapies a genuine health concern. Testosterone replacement therapy alone grew more than 24 percent from 2005 to 2009, the year it reached $838 million in annual sales [source: Research and Markets]. Before men add synthetic testosterone to their systems, they should undergo testing to be sure prostate cancer cells are present. About half of men age 50 and older probably have cancer cells lurking in their prostate [source: Harvard Medical School].

It also pays to pay attention to another hormone -- melatonin -- regardless of gender. This hormone regulates your internal clock, and is the reason you become sleepy at night and wakeful in the morning. Seemingly innocuous behaviors, such as sleeping with a lamp glowing or television playing, can put you at increased risk for cancer. That's because light exposure at night short circuits melatonin production and could prompt abnormal cell growth [source: Fox].

4

Men Experience "Menopause"

Late-stage andropause (after age 70), caused by lowering levels of testosterone, may also signal the progression of Alzheimer's disease.

Women aren't the only ones affected by depleting hormones. An estimated 4 million U.S. men have low levels of testosterone, a downward slide that begins at about age 40 [source: Brody]. Roughly equivalent to female menopause, the male version is dubbed "andropause" or "male menopause," and can wreak havoc on a man's weight, energy levels, moods and sex drive. Late-stage andropause, which occurs after age 70, may also signal the progression of Alzheimer's disease or even the penchant to develop age-related memory problems [source: Boyles].

Replacing testosterone with synthetic hormone medications is an option, but it's not a simple fix. In 2009, a federally financed study of men using testosterone gel screeched to a halt when a high rate of cardiac complications cropped up. In 2010, a $45 million study by the National Institute on Aging is studying testosterone treatments [source: Brody]. Pending any research-related revelations, men can turn to exercise and other lifestyle changes to help reduce weight, which can help them utilize testosterone more efficiently.

3

Testosterone Fuels Weight Loss

Few things are more frustrating than having a weight-loss battle with a man as your main competition. All things (including diet) being equal, men typically lose more weight than women. And they lose it faster. While it hardly seems fair, there's a physiological reason for their success: On average, they tote 40 pounds more muscle than women, and 10 times the testosterone. While the testosterone boosts metabolism, the increased muscle mass burns calories -- even while the body's resting [source: King]. The good weight-loss luck begins to wear off, eventually. As men hit age 40, testosterone production decreases -- to the tune of about three percent each year for the rest of their lives. This makes it harder to maintain a fat-burning metabolism and, conversely, makes it easier to gain weight. Plus, men with large midsections are more likely to have low testosterone levels than those rocking flat abs, which lends itself to a weight-gain cycle [source: Fisch].

2

Men have Monthly Cycles

Some scientists now think male hormones fluctuate monthly just like female hormones do and may cause mood changes.

There's plenty of information (official and anecdotal) about the wax and wane of female hormone levels throughout the month. But did you know that men's hormones rise and fall each month, too? These 30-day hormone cycles are still a controversial topic within the medical community, largely because there's not a lot of data to back up the idea. Still, it makes sense to many people that men probably experience monthly hormonal ups and downs that affects mood and energy levels. After all, there are seasonal, daily and even hourly deviations in hormone levels. Testosterone quantities can range up and down four or five times an hour, and are typically higher in the morning and lower at night. For many men, testosterone levels follow a seasonal pattern, too: They are increased in the fall and decreased in the spring. [source: Diamond]. Keeping track of mood fluctuations for 30 days will likely reveal an emotional pattern prompted by hormones; simply understanding what's behind one's attitude can make a big difference in daily interactions, as you'll read on the next page.

1

The MidLife Crisis has Hormonal Roots

For women, the loss of androgens (male hormones) begins surprisingly early -- before age 40 -- and results in fatigue, loss of bone mass and decreased sexual desire [source: Boston University School of Medicine]. For men, this gradual change usually peaks at age 50 and ushers in everything from male-pattern baldness to osteoporosis, which is a loss of bone density [source: Shmerling]. A reduction in androgens, which includes testosterone, can have emotional impacts as well. While recent research refutes the fact that male hormones make men act more aggressively, there is one stereotype that seems to hold true: The midlife crisis. About the time a man reaches age 50, he may become bored with his career, marital status or the American dream in general, but this emotional reaction has physiological roots [source: Fisch]. Rather than seeking a boost from a new sports car, most men would be better served by a simple blood test. That's because it can uncover potentially low testosterone levels, which may be the source of depression or dissatisfaction.

Krassas, Gerasimos. "Erectile Dysfunction in Patients with Hyper- and Hypothyroidism: How Common and Should we Treat?" Journal of Clinical Endocrinology and Metabolism. 93,05: 1815-1819. http://jcem.endojournals.org/cgi/content/full/93/5/1815

Shmerling, Robert. "Testosterone: What it Does and What Doesn't Do." (Oct. 12, 2010) MSN.com. http://health.msn.com/health-topics/sexual-health/mens-sexual-health/articlepage.aspx?cp-documentid=100200703